Magnetic disk apparatus and method of manufacturing the apparatus

ABSTRACT

A magnetic disk apparatus having a highly sensitive reproducing head and a method for manufacturing the magnetic disk apparatus are disclosed. A spin-valve-type multilayer film composed of an antiferromagnetic layer, a ferromagnetic layer, a nonmagnetic layer and a free magnetic layer is used as a magnetoresistive-effect device for the reproducing head. An antiferromagnetic reaction layer is formed between the antiferromagnetic reaction layer and the ferromagnetic layer. The antiferromagnetic reaction layer is formed of a metallic compound containing oxygen.

TECHNICAL FIELD

The present invention relates to a magnetic disk apparatus and a methodof manufacturing the magnetic disk apparatus and, more particularly, toa magnetic disk apparatus having a magnetoresistive-effect device usinga spin valve magnetoresistive effect, which device is used in areproducing head or a magnetic field sensor, and to a method ofmanufacturing the magnetic disk apparatus.

BACKGROUND ART

In recent years, the need to increase the processing speed and therecording capacity in recording on magnetic disk media in magnetic diskapparatuses (HDD apparatuses) or the like has increased. Schemes todevelop high-density magnetic recording media are now being contrivedand pursued. With this movement, reproducing heads used for reproductionfrom reproducing tracks of smaller widths and having larger reproductionoutputs in comparison with conventional thin-film magnetic heads arebeing developed. It is certain that this tendency will be accelerated infuture.

Spin-valve-type magnetoresistive-effect films are presently being usedordinarily in magnetoresistive-effect devices for reproducing heads. Aspin-valve magnetoresistive-effect film has a basic structure formed ofa free magnetic layer, a nonmagnetic layer, a fixed magnetic layer andan antiferromagnetic layer.

A structure designed to increase the recording density by increasing thesensitivity of such a spin-valve magnetoresistive-effect film is known.For example, Japanese Patent Laid-Open No. 6-236527 discloses astructure in which the thickness of a free magnetic layer is increasedand an electroconductive layer is formed adjacent to and at the back ofthe free magnetic layer to increase the mean free path.

Also, “Kamiguchi et al “CoFe SPECULAR SPIN VALVES WITH A NANO OXIDELAYER” Digests of Intermag 1999, DB-01, 1999” discloses a technique ofobtaining a so-called specular reflection effect by inserting between afree layer and a fixed magnetic layer an extremely thin oxide layercalled NOL (Nano Oxide Layer) and causing conduction electrons to bereflected by the interface between the oxide layer and a metal layer. Inthis arrangement, a spin valve film is formed like a pseudo artificialgrating film, whereby the MR ratio can be improved.

Japanese Patent Laid-Open No. 7-262520 discloses a report saying thatwhen a GMR device constituted by a multilayer film uses a CPP (currentperpendicular-to-the-plane) mode in which a current is caused to flowperpendicularly to a film surface, it has a change in resistance twicethat in the conventional CIP (current in-the-plane) mode in which acurrent is caused to flow parallel to the film surface. An increasingnumber of adaptations to CPP-spin valve films are being made.

Under circumstances where there will be a stronger demand for increasingthe recording density of magnetic recording media, there is a challengeto further increase the sensitivity of magnetoresistive films inmagnetoresistive-effect devices for reproducing heads in order toreproduce signals recorded at short wavelengths on magnetic recordingmedia.

DISCLOSURE OF THE INVENTION

In view of the above-described technical problem in the known art, anobject of the present invention is to implement a magnetic diskapparatus having a thin-film magnetic head improved in sensitivity bydevising the structure of a magnetoresistive-effect film used in amagnetoresistive-effect device for the magnetic disk apparatus, and amethod of manufacturing the magnetic disk apparatus.

A magnetic disk apparatus provided to achieve this object according to afirst aspect of the present invention is a magnetic disk apparatusincluding a magnetoresistive-effect device using amagnetoresistive-effect film which is a spin-valve-type multilayer filmconstituted by an antiferromagnetic layer, a ferromagnetic layer, anonmagnetic layer and a free magnetic layer, wherein anantiferromagnetic reaction layer is provided between theantiferromagnetic layer and the ferromagnetic layer, and theantiferromagnetic reaction layer is formed of a metallic compoundcontaining oxygen.

According to this arrangement, since the antiferromagnetic reactionlayer is provided between the antiferromagnetic layer and theferromagnetic layer in the magnetoresistive-effect film constituting themagnetoresistive-effect device, electrons can be reflected by theinterface between the antiferromagnetic reaction layer and the metalliclayer to increase the degree of diffusion of electrons, therebyobtaining a high MR ratio and achieving a higher recording density.

A magnetic disk apparatus in a second aspect of the present invention isa magnetic disk apparatus including a magnetoresistive-effect devicecapable of operating with a current direction perpendicular to the filmsurface (CPP mode) using a magnetoresistive-effect film which is aspin-valve-type multilayer film constituted by antiferromagnetic layers,ferromagnetic layers, nonmagnetic layers and a free magnetic layer,wherein an antiferromagnetic reaction layer is provided between theantiferromagnetic layers and the ferromagnetic layers, and theantiferromagnetic reaction layers are formed of a metallic compoundcontaining oxygen.

According to this arrangement, a high MR ratio can be obtained even in amagnetic disk apparatus having a magnetoresistive-effect deviceoperating in a CPP mode to achieve a higher recording density.

Preferably, in the first and second aspects of the present invention,the antiferromagnetic reaction layer is formed of a Mn-based metalliccompound containing oxygen, and the film thickness thereof is 0.1 to 2.5nm. Preferably, the antiferromagnetic reaction layer contains at leastone constituent selected from nitrogen, hydrogen and H₂O. Further,preferably, the antiferromagnetic reaction layer is formed by naturaloxidation or plasma oxidation.

Preferably, the antiferromagnetic layers are formed of a Mn-based alloycontaining at least one constituent selected from Pt, Ir, Ru and Rh, anda base layer under the antiferromagnetic layer is formed of NiFe orNiFeCr.

Preferably, the ferromagnetic layers and the free magnetic layer areformed of an alloy containing at least one of Fe, Co and Ni, and thenonmagnetic layers are formed of an alloy containing Cu. Further,preferably, the ferromagnetic layers are formed in a stackedferromagnetic structure constituted by a first ferromagnetic layer, ametallic intermediate layer and a second ferromagnetic layer, and themetallic intermediate layer is formed of an alloy containing at leastone constituent selected from Ru, Cu, Rh, Pd, Ag, Ir, Pt and Au.

According to the present invention, there are provided methods ofmanufacturing the magnetic disk apparatuses in the first and secondaspects. The first manufacturing method includes, to form themagnetoresistive-effect film as a film in which the antiferromagneticreaction layer is provided between the antiferromagnetic layer and theferromagnetic layer, conveying a substrate into a first chamber andforming the antiferromagnetic layer in a vacuum atmosphere in the firstchamber, conveying the substrate into a second chamber and performingvacuum discharge in the second chamber at a degree of vacuum lower thanthat in the first chamber to form the antiferromagnetic reaction layer,and taking out the substrate from the second chamber and forming theferromagnetic layer on the antiferromagnetic reaction layer in anotherchamber.

The second manufacturing method includes, to form themagnetoresistive-effect film as a film in which the antiferromagneticreaction layer is provided between the antiferromagnetic layer and theferromagnetic layer, conveying a substrate into a first chamber andforming the antiferromagnetic layer in a vacuum atmosphere in the firstchamber, conveying the substrate into a second chamber and performing asurface treatment using a gas containing 1 ppm or higher of H₂O or O₂ toform the antiferromagnetic reaction layer, and taking out the substratefrom the second chamber and forming the ferromagnetic layer on theantiferromagnetic reaction layer in another chamber.

Preferably, in the above-described first and second manufacturingmethods, the degree of vacuum in the first chamber is in the range from1×10⁻⁶ to 1×10⁻⁸ Pa.

The third manufacturing method includes, to form themagnetoresistive-effect film as a film in which the antiferromagneticreaction layer is provided between the antiferromagnetic layer and theferromagnetic layer, conveying a substrate into a first chamber andforming the antiferromagnetic layer in a vacuum atmosphere in the firstchamber, conveying the substrate into a second chamber and exposing thesubstrate to an atmosphere in which the H₂O concentration or the O₂concentration is higher than that in the first chamber to form theantiferromagnetic reaction layer, and taking out the substrate from thesecond chamber and forming the ferromagnetic layer on theantiferromagnetic reaction layer in another chamber.

Preferably, in the above-described first to third manufacturing methods,the substrate is exposed to the vacuum atmosphere in the second chamberfor a time period of 60 seconds or longer. Also, the method ispreferably such that, after the completion of the process in the secondchamber, the substrate is again conveyed into the first chamber and afilm forming process of forming the ferromagnetic layer and other layersis thereafter performed.

Each of the above-described first to third manufacturing methods can beeasily implemented by using a helicon long-throw sputtering apparatus.

According to the present invention, as described above, anantiferromagnetic reaction layer is formed between an antiferromagneticlayer and a ferromagnetic layer in a spin-valve-typemagnetoresistive-effect film having the antiferromagnetic layer, theferromagnetic layer, a nonmagnetic layer and a free magnetic layer toincrease the MR ratio of the magnetoresistive-effect device and tothereby obtain a higher head output. A magnetic disk apparatus havingsuch a high-sensitivity reproducing head is capable of realizinghigh-density recording and an increased recording capacity recently indemand.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged schematic sectional view of an essential portionof a reproducing head of a magnetic disk apparatus according toEmbodiment 1 of the present invention as seen from a head slide surfacefacing a magnetic recording medium;

FIG. 2 shows diagrams schematically depicting structures ofmagnetoresistive-effect films according to the embodiment;

FIG. 3 is an X-ray diffraction profile showing dependency of themagnetoresistive-effect film on a base material according to theembodiment;

FIG. 4 shows graphs depicting the results of measurement of MR ratios,respectively, of a conventional spin valve film and of a spin valve filmaccording to the embodiment;

FIG. 5 shows graphs depicting, respectively, the MR ratio with respectto the film thickness of a nonmagnetic layer according to theembodiment, and the dependency of an interlayer coupling magnetic fieldHint on the film thickness of the nonmagnetic layer;

FIG. 6 is an enlarged schematic sectional view of an essential portionof a reproducing head of a magnetic disk apparatus according toEmbodiment 2 of the present invention as seen from a head slide surfacefacing a magnetic recording medium;

FIG. 7 is a graph depicting the relationship between a junction area andthe resistance change rate in a GMR device according to the embodiment;

FIG. 8 is a plan view of a sputtering apparatus used in Embodiment 3 ofthe present invention;

FIG. 9 is a graph depicting the MR ratio with respect tostanding-in-vacuum time according to the embodiment; and

FIG. 10 is a graph showing the MR ratio with respect tostanding-in-vacuum conditions according to the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference tothe drawings. The present invention is not limited to the embodimentsdescribed below. The present invention can be applied to magnetic diskapparatuses having a magnetoresistive-effect devices usingspin-valve-type magnetoresistive-effect films.

EMBODIMENT 1

FIGS. 1 to 5 show Embodiment 1 of the present invention.

In a reproducing head of the magnetic disk apparatus shown in FIG. 1, alower gap insulating layer 2 formed of a nonmagnetic insulating materialsuch as Al₂O₃, AlN or SiO₂ is provided on a lower shield layer 1, whichis a magnetic film formed of, for example, a soft magnetic material suchas permalloy, a Co-based amorphous material, or Fe-based fine particles.A GMR device 3 is provided on the lower gap insulating layer 2. The GMRdevice 3, not shown in detail, is a multilayer film including anantiferromagnetic layer, a ferromagnetic layer, a nonmagnetic layer anda free magnetic layer. The structure of the GMR device 3 will beconcretely described below. Opposite side portions of the multilayerfilm forming the GMR device 3 are formed by etching processing such asion milling so that the film has the shape of a trapezoidal block havingslanted side surfaces. A pair of left and right hard bias layers 4 areprovided on opposite sides of the multilayer film. The hard bias layers4 are formed on the lower gap insulating layer 2 so as to contact atleast the opposite side surfaces of the free magnetic layer constitutingthe GMR device 3. The hard bias layers 4 are formed of a hard magneticmaterial, such as a CoPt-based alloy. A pair of left and right electrodelead layers 5 are formed of a material such as Cu, Cr or Ta on the hardbias so as to contact at least the GMR device 3 in a line contactmanner. An upper gap insulating layer 6 is formed on the pair of leftand right electrode lead layers 5 and the GMR device 3. The upper gapinsulating layer 6 is formed of the same insulating material as that ofthe lower gap insulating layer 2. An upper shield layer 7 formed of thesame soft magnetic material as that of the lower shield layer 1 isformed on the upper gap insulating layer 6.

As shown in FIGS. 2 a and 2 b, the GMR device 3 is constituted by a spinvalve type of magnetoresistive-effect film.

FIG. 2 a shows a spin valve film of a bottom-type spin valve structureformed of a base layer 11, an antiferromagnetic layer 12, anantiferromagnetic reaction layer 13, a ferromagnetic layer 14, anonmagnetic layer 15, a free magnetic layer 16 and a projective layer17.

FIG. 2 b shows a spin valve film of a dual spin valve structure formedof a base layer 11, a first antiferromagnetic layer 12, anantiferromagnetic reaction layer 13, a first ferromagnetic layer 14, afirst nonmagnetic layer 15, a free magnetic layer 16, a secondnonmagnetic layer 18, a second ferromagnetic layer 19, a secondantiferromagnetic layer 20 and a protective layer 17.

The antiferromagnetic layer 13 is thus provided between theantiferromagnetic layer 12 and the ferromagnetic layer 14 to increasethe MR ratio of the spin valve film and to thereby enable the head tohave a higher output.

Details of the spin valve film will be described.

The base layer 11 is used for the purpose of improving the adhesionbetween the lower gap layer 2 and the spin valve film and improving thealignment of the spin valve film. The base layer 11 is ordinarily formedof a Ta film. Preferably, for a further improvement in the alignment ofthe spin valve film, the base layer 11 is formed in a two-layerstructure: Ta layer/NiFe-based alloy layer for example.

To examine the influence of the base layer 11 on the spin valve film,the bottom-type spin valve film was formed on base layers 11 formed ofvarious materials and X-ray diffraction was effected. The spin valvefilm in this construction is the same as that in the conventional art.

FIG. 3 shows measurement results obtained.

In FIG. 3, the ordinate represents the strength and the abscissarepresents the diffraction angle. The case where the base layer 11 is aTa layer is indicated by (a), the case where the base layer 11 has atwo-layer structure: Ta layer/NiFe layer is indicated by (b), and thecase where the base layer 11 has a two-layer structure: Ta layer/NiFeCrlayer is indicated by (c).

Referring to an enlarged graph of SV (111) orientation in the regionsurrounded by the broken line, the diffraction peak of the spin valvefilm on the Ta base indicated by (a) is very weak, while the (111)diffraction peaks of the spin valve films on the two-layer structuresindicated by (b) and (c) are very high. Thus, it is apparent that thealignment of the spin valve film is improved if the base layer 11 isformed in a two-layer structure.

While the bottom-type spin valve film has been described by way ofexample, the same fact has been confirmed with respect to other spinvalve films including a spin valve film of a dual spin valve structure,Also, while a Ta single layer structure, a two-layer structure formed ofTa layer and a NiFe layer and a two-layer structure formed of Ta layerand a NiFeCr layer have been described as the base layer 11, the presentinvention is not limited to this example. The base layer 11 may beformed of any other material. Also, an arrangement without the baselayer 11 may be used.

The antiferromagnetic layer 12 plays the role of exchange coupling tothe ferromagnetic layer 14. In the spin valve film having a dual spinvalve structure, the first antiferromagnetic layer 12 plays the role ofexchange coupling to the first ferromagnetic layer 14, and the secondantiferromagnetic layer 20 plays the role of exchange coupling to thesecond ferromagnetic layer 19.

Preferably, each of the antiferromagnetic layers 12 and 20 is formed ofan Mn-based alloy. More preferably, an Mn-based alloy containing atleast one element selected from Pt, Ir, Ru and Rh. In the presentinvention, it is preferable to use an IrMn film in particular. The IrMnfilm can be formed by performing sputtering using a 20 at % Ir-80 at %Mn target so that a predetermined film composition is obtained under thecontrol at a sputtering argon gas pressure.

The antiferromagnetic reaction layer 13, which is a feature of thepresent invention, is for obtaining a high MR ratio by intensifying theinterlayer coupling magnetic field between the antiferromagnetic layer12 and the ferromagnetic layer 14. Preferably, the antiferromagneticreaction layer 13 is formed of a metallic compound containing oxygen.More preferably, the antiferromagnetic reaction layer 13 is formed of anMn-based metallic compound containing oxygen. A layer formed of such ametallic compound can be obtained by an oxidation process such asnatural oxidation or plasma oxidation.

Preferably, at least one element or compound selected from nitrogen,hydrogen and H₂O is contained as an additive element in theantiferromagnetic layer 13.

The thickness of the antiferromagnetic layer 13 is preferably in therange of 0.1 to 2.5 nm, more preferably in the range of 0.1 to 2.0 nm,most preferably in the range of 0.15 to 2.0 nm. If the thickness of theantiferromagnetic layer 13 exceeds 2.5 nm, the interlayer couplingmagnetic field between the antiferromagnetic layer 12 and theferromagnetic layer 14 is so weak that the MR ratio cannot besufficiently increased. If the thickness of the antiferromagnetic layer13 is smaller than 0.1 nm, a sufficiently high MR ratio cannot beobtained.

To check the MR ratio improving effect of the antiferromagnetic layer13, MR curves were measured with respect to the conventional spin valvefilm with no antiferromagnetic reaction layer and the spin valve film ofthe present invention having the antiferromagnetic reaction layer 13.

FIG. 4 a shows the MR curve of the conventional spin valve film, andFIG. 4 b shows the MR curve of the spin valve film of the presentinvention. In FIGS. 4 a and 4 b, the ordinate represents the MR ratioand H along the abscissa H represents the applied magnetic field.

Each spin valve film is of the dual type. Details of the spin valve filmare as described below.

The base layer 11 is [Ta layer (3 nm)/NiFeCr (3 nm)]; theantiferromagnetic layer 12 [IrMn layer (5 nm)]; the antiferromagneticlayer 13 in the case of the arrangement using the antiferromagneticlayer 13 [MnO₂ (1 nm)]; the ferromagnetic layer 14 [CoFe layer (2 nm)];the nonmagnetic layer 15 [Cu layer (2.3 nm)]; the free magnetic layer 16[CoFe layer (3 nm)]; the nonmagnetic layer 18 [Cu layer (2.3 nm)]; theferromagnetic layer 19 [CoFe layer (2 nm)]; the antiferromagnetic layer20 [IrMn layer (5 nm)]; and the protective layer 17 [Ta layer (3 nm)].The numeric values in the parentheses represent the thicknesses of thelayers.

As shown in FIG. 4 a, the MR ratio of the conventional spin valve filmhaving no antiferromagnetic layer was about 14%. On the other hand, theMR ratio of the spin valve film of the present invention in which theantiferromagnetic reaction layer 13 is provided is about 17%, higherthan that of the conventional spin valve film.

It can be understood that the MR ratio is increased if theantiferromagnetic reaction layer 13 is formed between theantiferromagnetic layer 12 and the ferromagnetic layer 14.

The ferromagnetic layer 14 couples to the antiferromagnetic layer 12 byexchange coupling, and the ferromagnetic layer 19 couples to theantiferromagnetic layer 20 by exchange coupling. Magnetization of theferromagnetic layers 14 and 19 is fixed in one direction by exchangecoupling.

Preferably, the ferromagnetic layers 14 and 19 are formed of an alloycontaining at least an element selected from Fe, Co and Ni. Morepreferably, CoFe is used in the present invention.

In the case where the spin valve film is of the dual type, a stackedferrimagnetic fixed magnetic layer may be formed to further heighten theexchange coupling between the ferromagnetic layers 14 and 19 and theantiferromagnetic layers 12 and 20. The stacked ferrimagnetic fixedmagnetic layer is a layer for artificially forming a stackedferromagnetic structure such that a Ru layer for example is providedbetween the first and second ferromagnetic layers 14 and 19 to make thedirections of magnetization of the first and second ferromagnetic layers14 and 19 reverse and parallel to each other. It has actually beenconfirmed that when the Ru film thickness is in the range from 0.5 to0.9 nm in the CoFe/Ru/CoFe system, the value of (residual magnetizationof Mr in the entire film)/(saturation magnetization of Ms) issubstantially zero and the directions of magnetization of the first andsecond ferromagnetic layers 14 and 19 are made reverse and parallel toeach other by means of the Ru layer. If such a construction is adopted,the thickness of the Ru layer is preferably 0.6 to 0.8 nm, morepreferably about 0.7 nm, i.e., in the range from 0.65 to 0.75 nm. Theintermediate layer inserted between the ferromagnetic layers 14 and 19is not limited to the Ru layer. At least one element selected from Cu,Rh, Pd, Ag, Ir, Pt and Au may be used for the intermediate layer. Also,the intermediate layer may be formed of an alloy containing a pluralityof components.

The first and second ferromagnetic layers 14 and 19 may be formed of thesame material or may be respectively formed of different materials.

The interlayer coupling magnetic field Hint between the first and secondferromagnetic layers 14 and 19 and the free magnetic layer 16 may beadjusted by setting a film thickness difference between the first andsecond ferromagnetic layers 14 and 19 or by setting a difference betweenthe values of the products (Ms×t) of the saturation magnetizations Msand the film thicknesses T of the ferromagnetic layers.

Preferably, the nonmagnetic layers 15 and 18 are formed of a Cu. Theinterlayer coupling magnetic field Hint between the first and secondferromagnetic layers 14 and 19 can be controlled by changing the filmthicknesses of the nonmagnetic layers 15 and 18.

A change in MR characteristic of the spin valve film due to a change infilm thickness of the nonmagnetic layers 15 and/or 18 is considerablylarge. For example, FIGS. 5 a and 5 b respectively show changes in MRratio of the spin valve film and changes in interlayer coupling magneticfield Hint between the fixed magnetic layer and the free magnetic layer16 in the bottom-type spin valve film of a film construction: Ta layer(3 nm)/NiFeCr layer (3 nm)/IrMn layer (5 nm)/CoFe layer (2 nm)/Cu layer(t nm)/CoFe layer (3 nm)/Ta layer (3 nm) when the film thickness of theCu layer is changed.

From FIGS. 5 a and 5 b, it can be understood that each of the MR ratioand the interlayer coupling magnetic field Hint is largely influenced bya small change in film thickness t of the Cu layer. The MR ratiodetermines the sensitivity of the spin valve film, and the interlayercoupling magnetic field Hint determines the bias point of the freemagnetic layer 16. The MR ratio and the interlayer coupling magneticfield Hint are each an important parameter.

Preferably, the free magnetic layer 16 is formed of an alloy containingat least one element selected from Fe, Co and Ni. It is necessary thatthe magnetization of the free magnetic layer 16 be comparatively freelyrotatable with respect to an external magnetic field, and the freemagnetic layer 16 needs to have a good soft magnetic characteristic. Forthe free magnetic layer 16, therefore, a Co-based alloy having a highercoefficient of diffusion at the interfaces on the nonmagnetic layers 15and 18 and not easily solid-soluble to the nonmagnetic layers 15 and 18is ordinarily used. However, the free magnetic layer 16 formed of aCo-based alloy has a rather bad soft magnetic characteristic and is itpreferable to use a CoFe-based alloy, more specifically Co₉₀Fe₁₀. Also,the free magnetic layer 16 may be formed in a two-layer structureconstituted by a magnetic layer formed of a Co-based alloy of a highdiffusion coefficient and a layer formed of a NiFe alloy having animproved soft magnetic characteristic other than a single-layerstructure. Further, a stacked free structure or a spin filter structurecomparatively advantageous in reducing the thickness of the freemagnetic layer 16 may be used.

The protective film 17 has a role to prevent the spin valve film frombeing oxidized by each of processes. In the present invention, Ta issuitably used for the protective film 17. The antiferromagnetic layers12 and 20 (Mn-based alloy) used in the spin valve film actually undergoa heat treatment process at a high temperature and are exposed to theatmosphere after lamination of the spin valve film for patternformation. Therefore, oxidation caused by such processes can beprevented if the protective film 17 is provided.

EMBODIMENT 2

FIGS. 6 and 7 show Embodiment 2 of the present invention.

Embodiment 2 differs from the above-described Embodiment 1 in that a GMRdevice 3 in a CPP mode is used.

In a reproducing head for a magnetic disk apparatus shown in FIG. 6, theGMR device 3 is formed under a lower shield layer 1, which is a magneticfilm formed of a soft magnetic material such as permalloy, a Co-basedamorphous material, or Fe-based fine particles, with a lower electrodelead layer 21 interposed between the GMR device 3 and the lower shieldlayer 1. In this case, Ta (3 nm)/Cu (300 nm)/Ta (50 nm) is used as thelower electrode lead layer 21

The spin valve film constituting the GMR device 3 is the same as thatdescribed in the above description of Embodiment 1. An upper electrodelead layer 22 formed of the same electroconductive material as that ofthe lower electrode lead layer 21 is provided on the GMR device 3. Thestructure is such that the GMR device 3 is sandwiched between the lowerelectrode lead layer 21 and the upper electrode lead layer 22. Tn thiscase, Ta (3 nm)/Cu (50 nm) is used as the upper electrode lead layer 22.

Front and rear side surfaces of the GMR device 3 are formed as slantedsurfaces by an etching method such as ion milling. A gap insulatinglayer 2 formed of a nonmagnetic insulating material such as Al₂O₃, AlNor SiO₂ is provided on the lower shield layer 1 on opposite sides of theGMR device 3.

A common shield layer 7 formed of the same soft magnetic material asthat of the lower shield layer 1 is provided so as to cover the uppersurfaces of the upper electrode lead layer 22 and the gap insulatinglayer 2, thus forming a device portion of the reproducing head.

In the device portion of the reproducing head constructed as describedabove, a current supplied from the lower electrode lead layer 21 flowsthrough the GMR device portion 3 to flow into the upper electrode leadlayer 22. A structure in which a supplied current flows through the filmin the GMR device 3 in a direction perpendicular to the film asdescribed above is called a CPP structure.

The CPP-GMR device constituted by the spin valve film of the presentinvention as described above and a CPP-GMR device constituted by theconventional spin valve film were operated to examine the relationshipbetween the GMR device 3—lower electrode lead layer 21 junction area Sand the resistance change rate ΔR. FIG. 7 shows the obtained measurementresults.

In the case of use of the spin valve film of the present invention inwhich the antiferromagnetic reaction layer 13 is formed between theantiferromagnetic layer 12 and the ferromagnetic layer 14, theresistance change rate ΔR is increased, as indicated by round marks inFIG. 7, in comparison with that in the case of use of the conventionalspin valve film indicated by triangular marks.

The GMR device operates in the CPP mode and uses the spin valve film inwhich an antiferromagnetic reaction layer is provided between theantiferromagnetic layer and the ferromagnetic layer. The resistancechange rate is thereby increased to obtain a higher head output.

EMBODIMENT 3

FIGS. 8 to 10 show Embodiment 3 of the present invention. As thisembodiment, a method of fabricating the spin valve film constituting theGMR device portion of the reproducing bead in the above-describedembodiments will be described.

An apparatus for film forming for the spin valve is not limited to aparticular one. A conventional well-known film forming apparatus can beused. A description will be made of a case of using a helicon long-throwsputtering apparatus will be described by way of example, because it issuitable for forming a magnetic film. A feature of the heliconlong-throw sputtering apparatus resides in that discharge at a lower gaspressure is possible. Accordingly, the mean free path of fine particlesdriven out from the target surface is increased, so that a sufficientlyhigh film forming rate can be obtained even if the distance between thetarget and the substrate is increased. The method of increasing thedistance between the target and the substrate has the effect of aligningthe angle of incidence fine particles flying to the substrate surfacewith a vertical direction. During film forming of the magnetic filmconstituting the spin valve film, fine particles flying to the substratesurface in an oblique direction may act to impair the magneticcharacteristics. Therefore, it is desirable that film forming beperformed by using mainly particles flying to the substrate surface inthe direction perpendicular to substrate surface during film forming ofthe magnetic film.

FIG. 8 shows the helicon long-throw sputtering apparatus.

A conveyance chamber 27 in which a conveyance device such as aconveyance arm (not shown) for conveying substrates one after anotherinto each of chambers described below is provided at a center of theapparatus. A load/locking chamber 23 for carrying substrates into thesputtering apparatus, a sputtering etching device 24, a high vacuumchamber 25 and a low vacuum chamber 26 are disposed around theconveyance chamber 27. Substrates are successively conveyed to thechambers by the conveyance device provided in the central conveyancechamber 27 and a multilayer film is continuously formed in vacuums.

In the high vacuum chamber 25, only an inert gas such as Ar is used as asputtering gas and the degree of vacuum to be reached is about 1×10⁻⁷Pa. In the low vacuum chamber 26, sputtering is performed by using atarget containing an impurity such as an oxide and by using a gas (e.g., O₂ and N₂) other than an inert gas such as Ar as a sputtering gas.The degree of vacuum to be reached the low vacuum chamber 26 is about1×10⁻⁶ Pa.

The method of fabricating the spin valve film by using the sputteringapparatus arranged as described above will be described. The sputteringfilm having the dual spin valve structure shown in FIG. 2 b inEmbodiment 1 described above was fabricated. The structure of thesputtering film is Ta layer/NiFeCr layer/IrMn layer/antiferromagneticreaction layer/CoFe layer/Cu layer/CoFe layer/Cu layer/CoFe layer/IrMnlayer/Ta layer. A sputtering target having a diameter of 5 inches wasused.

First, a substrate was placed in the load/locking chamber 23 andevaluation in the load/locking chamber 23 was performed until thedesired degree of vacuum was reached. The degree of vacuum to be reachedwas set to 1.0×10⁻⁴ Pa or lower. After reaching the desired degree ofvacuum, the substrate was taken out of the load/locking chamber 23, wasthen conveyed into the sputtering etching device 24, and underwent asurface treatment on impurities on the substrate surface.

The substrate surface-treated was taken out of the sputtering etchingdevice 24 and conveyed into the high vacuum chamber 25. The base layer11 was formed and film forming of the spin valve film was successivelyperformed.

Film forming of the spin valve film will be concretely described. First,the first antiferromagnetic film 12 was formed on the substrate in thehigh vacuum chamber 25.

Subsequently, the substrate was taken out from the high vacuum chamber25, was then conveyed into another chamber, which was the load/lockingchamber 23 in this case, to be left standing for a desired time periodin the vacuum at a degree of vacuum lower than the degree of filmforming vacuum in the high vacuum chamber 25, thereby performing filmforming of the antiferromagnetic reaction layer 13.

The degree of vacuum in the high vacuum chamber 25 is not particularlyspecified. However, it is preferably in the range from 1×10⁻⁶ to 1×10⁻⁸Pa.

After film forming of the antiferromagnetic reaction layer 13, thesubstrate was again conveyed into the high vacuum chamber 25 and thefirst ferromagnetic layer 14, the first nonmagnetic layer 15, the freemagnetic layer 16, the second nonmagnetic layer 18, the secondferromagnetic layer 19, the second antiferromagnetic layer 20 and theprotective layer 17 were formed by well-known conventional techniques.The spin valve film having the dual spin valve structure was therebyfabricated. The above-described sequence of spin valve film formingprocess steps is performed without any break in the maintenance of thevacuum atmosphere.

The substrate on which the antiferromagnetic layer 12 is formed is takenout from the high vacuum chamber 25 and left standing in theload/locking chamber 23 having a lower degree of vacuum as describedabove, thus enabling the antiferromagnetic reaction layer 13 to beeasily formed.

FIG. 9 is a graph showing the relationship between the time during whichthe substrate after film forming of the antiferromagnetic layer 12 wasleft standing in the load/locking chamber 23 and the MR ratio of theobtained spin valve film.

In FIG. 9, triangular marks indicate the substrate immediately afterfilm forming of the spin valve film, and round marks indicate the MRratio of the substrate taken out from the chamber after the completionof film forming of the spin valve film and processed by a heat treatment(annealing) in a vacuum using a well-known annealing apparatus underconditions: 200° C., 2.5 hours, and an applied magnetic field of 240kA/m.

During measurement, the degree of vacuum in the high vacuum chamber 25was set to 6.0×10⁻⁸ Pa and the degree of vacuum in the load/lockingchamber 23 was set to 3.0×10⁻⁶ Pa.

Table 1 shows data corresponding to that shown in FIG. 9. TABLE 1Surface Not annealed Annealed treatment time MR MR (second) (%) (%) 09.4 14.09 60 13.54 17.47 80 13.96 17.05 150 14.94 17.65 300 14.43 18.13

The conventional spin valve film with no antiferromagnetic reactionlayer corresponds to the standing time 0 second in FIG. 9. The MR ratioof the film not annealed after the formation of the antiferromagneticlayer 12 was about 9.5%, while the MR ratio of the annealed film wasabout 14%.

In contrast, in the case of the spin valve film on which theantiferromagnetic reaction layer 13 was formed by the above-describedfabrication method of the present invention, the MR ratio after filmforming was increased by about 15% and the ME ratio after annealing wasincreased by about 18%.

Thus, in the present invention, the antiferromagnetic reaction layer 13can be formed by the process including standing in a vacuum and, as aresult, a spin valve film having a higher MR ratio can be obtained. Thefilm thickness of the antiferromagnetic reaction layer 13 can becontrolled through the degree of vacuum at which standing in a vacuum iscontinued and the standing time.

FIG. 10 is a graph showing the relationship between different degrees ofvacuum at which standing after film forming of the antiferromagneticlayer 12 was continued and the standardized MR ratio of the spin valvefilm. A to E on the abscissa indicate conditions after film forming ofthe antiferromagnetic layer 12. Triangular marks in the graph indicatethe results with respect to those not annealed, while round marksindicate the results with respect to those annealed.

A: The spin valve film was grown by the conventional continuous filmforming method.

B: After film forming of the antiferromagnetic layer 12, the substratewas temporarily exposed to the atmosphere and the spin valve film wasthereafter grown.

C: The substrate was temporarily taken out from the chamber during thetime period from film forming of the antiferromagnetic layer 12 toforming of the ferromagnetic layer 14, underwent a heat treatmentprocess in a vacuum in another annealing apparatus, and was againreturned to the chamber under the same condition as before, followed byfilm forming of the spin valve film.

D: After film forming of the antiferromagnetic layer 12, the substratewas conveyed into the load/locking chamber 23 and exposed to a vacuumatmosphere (8×10⁻⁸ Pa) at a degree of vacuum higher than that in thehigh vacuum chamber 25, and the spin valve film was grown after thisprocess.

E: After film forming of the antiferromagnetic layer 12, the substratewas conveyed into the load/locking chamber 23 and exposed to a vacuumatmosphere (3.0×10⁻⁶ Pa) at a degree of vacuum lower than that in thehigh vacuum chamber 25, and the spin valve film was grown after thisprocess.

As shown in FIG. 10, the spin valve film obtained by leaving thesubstrate standing in the atmosphere as under the condition B and thespin valve film processed by a heat treatment as under the condition Chave a rather reduced MR ratio in comparison with the conventional spinvalve film under the condition A. Exposure of the substrate to ahigh-vacuum atmosphere as under the condition D more or less increasesthe MR ratio but the effect of increasing the MR ratio is notsubstantially high.

In contrast, the MR ratio of the spin valve film obtained under thecondition E by using the manufacturing method of the present invention,i.e., by exposing the substrate to a low-vacuum atmosphere, is increasedby about 25 to 50% relative to that of the conventional spin valve filmunder the condition A.

That is, for the formation of the antiferromagnetic reaction layer 13,exposure of the substrate to a vacuum atmosphere at a degree of vacuumlower than that in the high vacuum chamber 25 for forming theantiferromagnetic layer 12. Preferably, exposure to a vacuum atmosphereat 1×10⁻⁷ Pa or higher is required.

In the present invention, another method effective in forming theantiferromagnetic reaction layer 13 other than the above-describedmethod is conceivable in which, after film forming of theantiferromagnetic layer 12, the substrate is conveyed into a chamberhaving an H₂O or O₂ concentration higher than that in the film formingprocess chamber (high vacuum chamber 25) before film forming of theferromagnetic layer 14, exposed to this atmosphere for about several tenseconds, and thereafter returned to the film forming process chamber,followed by film forming of the ferromagnetic layer 14 and the otherlayers.

Another method further effective in forming the antiferromagneticreaction layer 13 is also conceivable in which, after film forming ofthe antiferromagnetic layer 12, the substrate undergoes a surfacetreatment by a gas containing 1 ppm or higher of H₂O or O₂ and isthereafter returned to the sputtering film forming chamber, followed byfilm forming of the ferromagnetic layer 14 and the other layers. Thesubstrate surface processing time in this method is not particularlyspecified but it is preferable to set the surface processing time to 60seconds or longer because a saturation region is reached it the surfaceprocessing time is about 60 seconds, as shown in FIG. 9 and Table 1, asis apparent from the relationship between the surface processing timeand the MR ratio (%) proportional to the head output.

While the process of forming the spin valve film including againreturning the substrate on which the antiferromagnetic reaction layer 13is formed to the high vacuum chamber 25 has been described, the presentinvention is not limited to this process. Film forming in a chamberdifferent from the high vacuum chamber 25 may alternatively beperformed.

1. A magnetoresistive-effect device comprising: amagnetoresistive-effect device using a magnetoresistive-effect filmwhich is a spin-valve-type multilayer film constituted by anantiferromagnetic layer (12); a ferromagnetic layer (14); a nonmagneticlayer (15); and a free magnetic layer (16), wherein an antiferromagneticreaction layer (13) is provided between the antiferromagnetic layer (12)and the ferromagnetic layer (14), and the antiferromagnetic layer (12)is formed of a metallic compound containing oxygen.
 2. Amagnetoresistive-effect comprising: a magnetoresistive-effect devicecapable of operating with a current direction perpendicular to the filmsurface (CPP mode) using a magnetoresistive-effect film which is aspin-valve-type multilayer film constituted by antiferromagnetic layers(12, 20); ferromagnetic layers (14, 19); nonmagnetic layers (15, 18);and a free magnetic layer (16), wherein an antiferromagnetic reactionlayer (13) is provided between the antiferromagnetic layers (12, 20) andthe ferromagnetic layers (14, 19), and the antiferromagnetic layers (12,20) are formed of a metallic compound containing oxygen.
 3. Themagnetoresistive-effect according to claim 1, wherein theantiferromagnetic reaction layer (13) is formed of a Mn-based metalliccompound containing oxygen, and the film thickness thereof is 0.1 to 2.5nm.
 4. The magnetoresistive-effect device according to claim 3, whereinthe antiferromagnetic reaction layer (13) contains at least oneconstituent selected from nitrogen, hydrogen and H₂O.
 5. Themagnetoresistive-effect device according to claim 1, wherein theantiferromagnetic reaction layer (13) is formed by natural oxidation orplasma oxidation.
 6. The magnetoresistive-effect device according toclaim 1, wherein the antiferromagnetic layers (12, 20) are formed of aMn-based alloy containing at least one constituent selected from Pt, Ir,Ru and Rh, and a base layer (11) under the antiferromagnetic layer (12)is formed of NiFe or NiFeCr.
 7. The magnetoresistive-effect deviceaccording to claim 1, wherein the ferromagnetic layers (14, 19) and thefree magnetic layer (16) are formed of an alloy containing at least oneof Fe, Co and Ni, and the nonmagnetic layers (15, 18) are formed of analloy containing Cu.
 8. The magnetoresistive-effect device according toclaim 1, wherein the ferromagnetic layers (14, 19) are formed in astacked ferromagnetic structure constituted by a first ferromagneticlayer (14), a metallic intermediate layer and a second ferromagneticlayer (19), and the metallic intermediate layer is formed of an alloycontaining at least one constituent selected from Ru, Cu, Rh, Pd, Ag,Ir, Pt and Au. 9.-15. (canceled)